Particulate Matter Migration in Subway Tunnels: Experimental and Numerical Investigation

Platform screen door (PSD) systems can reduce particulate matter (PM) levels at subway platforms, but transient particle migration between tunnels and platforms still occurs during door operation. Existing control measures, such as tunnel cleaning, ventilation optimization, onboard dust removal devices, and air curtain systems, mainly target background PM concentrations and generally function as passive mitigation strategies. However, the transient dynamics of tunnel-to-platform PM migration during PSD operation remain insufficiently understood. In this study, field measurements and numerical simulations were used to investigate PM migration under realistic subway operating conditions. Field observations were conducted to characterize the spatial distribution of PM and its relationship with tunnel piston wind. A numerical model based on the Discrete Phase Model (DPM) was then developed to simulate particle transport under different PSD operating sequences. The effects of PSD opening delay and opening duration on particle migration were examined to evaluate their influence on migration rates. The results show that adjusting the timing of PSD operation can significantly reduce tunnel-to-platform PM migration, whereas conventional air curtain configurations may enhance interzonal particle exchange under certain conditions. These findings improve the understanding of PSD-related PM transport and provide potential operational strategies for improving air quality in underground rail transit systems.